Thousands of leopard sharks and other marine life including rays, striped bass and smooth-hound sharks have been dying in the San Francisco Bay.
Researchers say that the deaths may be due to a parasite that enters via the nose and eats the brain slowly.
While the parasite is deadly to sharks and other marine animals, it is unlikely that humans who swim in the bay or who eat infected animals will become infected themselves.
Between February and July of 2017, the California Department of Fish and Wildlife estimates that 1,000-2,000 leopard sharks died in the San Francisco Bay
The findings, revealed in an NBC Bay Area Investigative Unit report, suggest that up to 2,000 leopard sharks have died in the San Francisco Bay of the last few months.
Dr Mark Okihiro, a researcher with the California Department of Fish and Wildlife, told NBC that the pathogen can affect a range of different species, killing species such as bat rays, striped bass, smooth-hound sharks and halibut.
‘We’re pretty confident at this point,’ Dr Okihiro said.
‘It’s called Miamiensis avidus.
‘It’s a small single celled organism.
‘It’s very similar to the common amoeba,’ he said.
WHY THE SHARKS ARE DYING
Thousands of leopard sharks and other marine life including rays, striped bass and smooth-hound sharks have been dying in the San Francisco Bay.
Researchers say that the deaths may be due to a parasite called Miamiensis avidus.
The parasite – a small, single-celled organism – enters via the nose and eats at the brain slowly.
While the parasite is deadly to sharks and other marine animals, it is unlikely that humans who swim in the bay or who eat infected animals will become infected themselves.
Miamiensis avidus. The parasite – a small, single-celled organism – enters via the nose and eats at the brain slowly. Scale bars = 5 µm
Dr Okihiro says he performs necropsies on dead, stranded sharks along the bay, along with researchers at UC San Francisco, to analyze the parasite DNA in thee sharks.
As the parasite slowly eats away that the brain, it causes the sharks to swim in circles or beach themselves, says Dr Okihiro.
Between February and July of 2017, the California Department of Fish and Wildlife estimates that 1,000-2,000 leopard sharks died in the San Francisco Bay.
As the parasite slowly eats away that the brain, it causes the sharks to swim in circles or beach themselves. Pictured are several sharks and a bat ray after washing up dead in the San Francisco Bay, photographed on April 26, 2017
However, because sharks are not buoyant and tend to sink when they’re not swimming, many dead sharks may sink to the sea floor and never wash up on the shore.
As such, Dr Okihiro says that leopard shark deaths may be higher than current estimates.
Because sharks are not buoyant and tend to sink when they’re not swimming, many dead sharks may sink to the sea floor and never wash up on the shore
Dr Andrew Nosal, a marine biologist at UC San Diego, told NBC that it’s important to determine what is killing the sharks because the deaths could start occurring down the coast of California.
In addition, the death of leopard sharks may have a knock-on effect on the ecosystem.
While it is not Dr Okihiro’s job to research why the sharks are dying, he has been researching them in his own time, performing necropsies in his kitchen living room and patio.
Leopard sharks aren’t threatened or endangered, and the California Department of Fish and Wildlife is not allocating any funds towards finding the cause of the shark deaths
He says that more resources are needed to study the matter, however, funds are limited at the California Department of Fish and Wildlife.
Gabe Tiffany, Deputy Director of Administration at the California Department of Fish and Wildlife, told NBC that the department has constraints on how its programs are funded.
Leopard sharks aren’t threatened or endangered, and the department is not allocating any funds towards finding the cause of the shark deaths.
Instead, it’s focusing on implementing the Marine Life Protection Act and rebuilding fisheries such as Chinook salmon in-river and the ocean, amongst other issues.